A fuller understanding of the operation of the demolition apparatus of the present invention may be achieved by studying U.S. Pat. No. 4,519,135, hereby incorporated by reference. This invention relates to a heavy duty demolition apparatus, especially adapted to be mounted on a rigid boom of a mobile vehicle and particularly adapted to be mounted on the dipper stick of an excavator, with a blade stabilizing device to keep the upper jaw of the apparatus from moving laterally relative to the lower jaw and breaking during the shearing operation on a workpiece.
The invention also has a replaceable crushing and shearing tip on the movable upper jaw.
Heavy duty shears of the type that are powered by hydraulic cylinders are proving more and more useful in handling scrap and especially metal scrap of all sorts. Such scrap comes in many different forms, and may be in the form of pipes made of steel or soft iron or cast iron, ranging in sizes from 2 inches or smaller, and up to 8 or 10 inches in diameter or larger; structural beams such as I-beams, channels, angle beams in a large range of sizes, up to 8 or 10 inches across and larger; rods and heavy cables having diameters of 2 to 3 inches and larger, metal sheets and plates and formed metal of all sorts including wheels and automobile and truck frames, and a myriad of long and short pieces of stock and metal pieces that are cast, rolled, stamped or otherwise formed, both singly and in various types of assembly.
The prior art has included numerous shears such as that illustrated in U.S. Pat. No. 4,198,747; U.S. Pat. No. 4,188,721; U.S. Pat. No. 4,897,921; U.S. Pat. No. 4,543,719; U.S. Pat. No. 4,558,515 and U.S. Pat. No. 4,104,792. Typically, these heavy duty shears mount on the dipper stick of an excavator so that the shears may be controlled fairly well in handling various types of scrap and cutting the scrap into smaller twisted and contorted pieces and lengths as the scrap is drawn into the throat of the shear.
Typically, these shears have a fixed lower jaw and a movable upper jaw that pivots on the lower jaw, with shear blades of hardened steel on both the upper jaw and the lower jaw. The workpiece is sheared by closing the upper jaw against the lower jaw under hydraulic pressure, with the shear blades cutting the workpiece. The movable upper jaw may also have a fixed, hardened shearing tip integral with the upper jaw. The tip is not suitable for removal and replacement due to the high lateral forces exerted on the tip as the movable jaw flexes laterally. Great tension is also exerted upon the tip, which may be wedged tight with scrap, upon opening the jaws. Direct shear bearing loads are also on the tip when shearing. All these factors will cause a removable tip to readily break off the upper jaw.
As stated, great lateral as well as vertical pressures develop against the movable upper jaw as it contacts and proceeds to cut the workpiece. This lateral pressure can cause the upper jaw to crack or otherwise experience structural failure. The lateral pressure exists from the moment the upper jaw contacts the workpiece until the workpiece is cut and the upper jaw meets the lower jaw and becomes supported by the lower jaw in a slot in the lower jaw. This lateral force develops analogously to when a person tries to cut too heavy an object with a pair of scissors. The scissors' blades are forced laterally apart and may break.
There is a need for a heavy duty demolition shear with a blade stabilizing device that prevents lateral movement of the upper jaw relative to the lower jaw and which supports the upper jaw against this lateral pressure. Such a shear should produce relatively clean or flat pieces of scrap which will allow the reduced scrap to stack and allow for more reduced scrap wad density.
In rebuilding highways for motor vehicle travel, and in the demolition of structures which are largely made of or incorporate reinforced concrete as structural members, the disposal of large pieces of concrete paving or reinforced concrete structure becomes a significant problem. Many governmental regulations and practical considerations relating to the operation of landfills prohibit the disposal of concrete slabs and large reinforced concrete structures by simply burying them in the landfills. Accordingly, it becomes necessary to dispose of such concrete material in other ways.
Crushing of the concrete is one alternative so that the concrete slabs and structures may be reduced to smaller particle sizes which accommodates the reuse of such concrete as fill and as aggregate base for roadways and the like.
It has been possible in the past to reduce concrete into particles and chunks by use of heavy duty shears, but such shears which are primarily designed for shearing steel and other metallic and wood structures have sharpened blades and are rather expensive for the purpose of reducing concrete slabs and structures which is thought to be accomplished in other ways. Such crushers are shown in U.S. Pat. Nos. 5,478,019; 4,512,524; 5,183,216; 5,044,569; and 4,951,886. Many of these crushers have crushing teeth rather than shearing blades.
Furthermore, crushing concrete may result in the development of lateral pressure against the movable upper jaw of a demolition shear in the same way that shearing metal does.
There is a need for a demolition shear apparatus with a replaceable crushing and shearing tip for both crushing concrete and shearing scrap metal.